Thickened inorganic oxidizer salt slurried explosive containing an alkylamine nitrate and an air-entrapping material



United States ABSTRACTDF DISCLOSURE. =Thickened slurry explosivecompositions containing an inorganicnitrate oxidizing salt, a loweralkylamine nitrate; water, as sensitizer a non-explosive,finely-divided, airentrappingmaterial and a thickening agent. Theseexplosive compositions are useful in small bore hole blastingoperations.

'BRIEF SUMMARY OF THE INVENTION .This invention relates to thickenedslurry explosive compositions. comprising an inorganic nitrate oxidizingsalt, a lower alkylamine nitrate, water, as sensitizer a non-explosive,finely-divided, air-entrapping material, and thickening agent.,ln aparticular aspect, this invention relates to thickened slurry. explosivecompositions having high rates on detonation, high brisance and suitablefor use in-small bore hole blasting operations, said compositioncontaining an inorganic nitrate oxidizing salt, a lower alkylaminenitrate; water, thickening agent, and as sensitizer anon-explosive,finely-divided, air-entrapping material.

The use in explosive compositions of inorganic nitrate sa1ts,,such asthe alkali metal nitrates, the alkaline earth metal nitrates, and inparticular ammonium nitrate, has become widespread in the mining andquarrying arts. For example, thickened aqueous slurries containingammonium nitrate have found extensive use in many blasting operations.

Even though explosive compositions such as those described above haveproven effective for numerous uses, such compositions are generally notsuitable as explosives for use in small bore hole applications unlesssensitized by a sensitizerwhich is itself a high explosive, such as forexample trinitrotoluene (TNT). The principal reason forthis is thatwithout the employment of a high explosive sensitizer the detonationvelocities of such compositions are not sufficiently high to give thedesired results. For reasons 'of economy and, more importantly, forreasons ofsafety, it is desirable to avoid the use of high explosivesensitizers in ammonium nitrate containing explosive compositions.

It is an object of the present invention to provide thickened explosivecompositions containing an inorganic nitrate oxidizing salt, a loweralkylamine nitrate, water, thickening agent, and a non-explosivesensitizer.

It is a further object of the present invention to provide thickenedslurry explosive compositions containing an inorganic nitrate oxidizingsalt, a lower alkylamine nitrate, water, a thickening agent, and anon-explosive sensitizer which have high rates of detonation, highbrisance and are suitable for use in small bore hole blastingoperations.

Other objects and advantages of the present invention will be apparentfrom the specification and appended claims.

The present invention resides in the discovery that explosivecompositions having high rates of detonation, high brisance and suitablefor use in small bore hole blasting operations are prepared by formingan admixture atent of from about 10 to about 90% by weight of aninorganic nitrate oxidizing salt, from about 5 to about 50% by Weight ofa lower alkylamine nitrate or mixtures of lower alkylamine nitrates, athickening agent, and a sensitizing amount of a non-explosive,finely-divided, air-entrapping material, the said weights being based onthe total weight of the nitrate salt, the water and the lower alkylaminenitrate. Such compositions are of low volatility and may be safelystored under standard storage conditions over long periods'of time.

The detonation rate'of an explosive composition is the rate at which thedetonation front passes through the explosive material. Detonation rateis typically expressed in feet per second. For the purpose of thepresent invention, high detonation rates are generally considered to bein excess of 14,000 feet per second. The compositions of the presentinvention have detonation rates in excess of 16,000 feet per second,with detonation'rates in excess of 20,000 feet per second beingreasonably common.

D tailed description Any suitable lower alkylamine nitrate, for instancelower alkylamine nitrates having from 1 up to about 8 carbon atoms, maybe used in the present invention. Included among such lower alkylaminenitrates are methylamine nitrate, ethylamine nitrate, propylaminenitrate, butylamine nitrate, octylamine nitrate, and the like. Becauseof its ready availability and the excellent results obtained therewith,methylamine nitrate is preferred in the present invention.

The lower alkylamine nitrate is employed in the compositions of thepresent invention in an amount in the range of from about 5 to about50%, with an amount in the range of from about 10 to about 35% beingpreferred.

Any suitable inorganic nitrate oxidizing salt or mixture of two or moresuch salts may be employed in the compositions of the present inventionwith ammonium nitrate being preferred when methylamine nitrate is thelower alkylamine nitrate. When sodium nitrate or mixtures of sodiumnitrate and ammonium nitrate are employed, a lower alkylamine nitrateother than methylamine nitrate is preferred. The form and particle sizeof amonium nitrate (or other salt) are not critical features of thepresent invention. For example, low density and high density ammoniumnitrate prills as well as ground or granular ammonium nitrate may beemployed. Preferably, the particle size of the nitrate salt issufiiciently small to pass a 20 mesh screen.

As previously indicated, the inorganic nitrate oxidizing salt isemployed in an amount in the range of from about 10 to about with anamount in excess of 40% being preferred.

The water content of the compositions of the present invention is suchas to dissolve all or a portion of the inorganic nitrate salt. Water isemployed in the compositions in an amount in the range of from about 5to about 50%, with an amount in the range of from about 5 to about 30%being preferred.

The sensitizers employed in th compositions of the present invention arenon-explosive, finely-divided, airentrapping materials. Examples of suchsensitizers include resin balloons, bagasse, wood flour, cork, balsa,and the like. Resin balloons of use as sensitizers in the compositionsof the present invention are water-insoluble, thinwalled, hollow,spherical balloons of a polymerized thermosetting resin selected fromthe group consisting of urea formaldehyde and phenol formaldehyde. Suchresin balloons are commercially available and are more fully describedin US. Patent 3,101,288 to Coursen et al., issued Aug. 20, 1963.

The amount of non-explosive sensitizer required to sensitize thecompositions of the present invention will ticular sensitizer employedand the degree of sensitization desired. Generally, an amount in therange of from about 0.1 to about 6.0% by weight is suitably employed,with amounts in the range of from about 0.4 to about 3.0% beingpreferred, the weights based on the total weight of the composition.

The class of materials used as thickeners for aqueous inorganic nitrateoxidizing salt explosive compositions is known and is illustrated bysuch materials as guar gum, gum Arabic, pregellatinized starch andcarboxymethyl cellulose, with guar gum being preferred. The amount ofthickening agent employed in the composition of the present inventionwill, of course, depend upon the particular thickening agent and theviscosity desired for the particular composition. An amount ofthickening agent in the range of from about 0.5 to about 5.0% by weightbased on the weight of the total composition is typically employed.

The compositions of the present invention may optionally contain, forexample, a metal powder, such as aluminum, to enhance their power, acarbonaceous material, such as fuel oil, to provide oxygen balance whenrequired, and a nitroparaflin, such as nitromethane, to obtain higherbrisance.

The compositions of the present invention are prepared by known mixingprocedures. The lower alkylamine nitrates are soluble in water, and ifdesired, may first be dissolved in water before mixing with otheringredients. The compositions may be safely manufactured, stored andshipped and hence may be prepared in a processing plant and transportedto the blasting site. If desired, the compositions may also be preparedat the site.

The compositions of the present invention are resistant to water, makingthem useful in wet as well as dry holes. The compositions require nocontainer even in wet holes. They displace water and maintain theirintegrity without dilution for extended periods of time beforedetonation. The compositions have a density in excess of 1.0 and becauseof this high density possess high bulk strength.

The compositions of the present invention are detonated in the knownmanner by conventional booster systems, such as for example Pentolite,Composition B, RDX, and the like. The amount of booster is determined inaccordance with known practice in the use of the particular boosterchosen.

The invention will be understood more fully by reference to thefollowing specific examples. It is understood that the examples arepresented for the purpose of illustration only and are not intended as alimitation of the invention.

Example 1 A series of runs was conducted in which the detonationvelocities of thickened slurry explosive compositions having ingredientsin the parts by weight indicated in Table 1 were determined. In the runsground ammonium nitrate of particle size sufficiently small to pass a 20mesh screen was employed. Detonation was accomplished with one-halfpound Composition B boosters. In the table all parts are by weight.

gum were then individually added to the solution under mixing.- Mixingwas then continued until'a composition of substantially uniformviscosity was obtained. The mixing procedure was carried out at roomtemperature.

Example 2 Explosive compositions similar to those of Example 1 areshownin-Table 2.

- TABLE 2 Composition G H I Sodium nitrate. 50. 55. 0 60. 0

a r 15.0 15. 0 15. 0 Bagasse 2.0 2.0 2.0 Guar gum 1. 2 1. 2 1. 2Ethylamine nitrate 31. 8 Propylamine nitrate 26.8 Octylamine nitrate 218 Since many embodiments of this invention may be made and since manychanges may be made in the embodiments described, the foregoing is to beinterpreted as illustrative only and the invention is defined by theclaims appended hereto.

I claim:

1. A thickened slurry explosive composition comprising:

(a) from about 10 to about 90% by weight of an inorganic nitrateoxidizing salt,

(b) from about 5 to about 50% by weight of a lower alkylamine nitrate,

(c) from about 5 to about 50% by weight of water,

(d) a non-explosive, finely divided, air-entrapping sensitizing materialselected from the group consisting of thin-walled, hollow, sphericalballoons, bagasse, wood flour, cork, and balsa in amounts sufiicient tosensitize the composition,

(e) a thickening agent in amounts sufficient to thicken the composition,

said weights being based on the total of the Weights of the nitratesalt, the lower alkylamine nitrate and the water.

2. The composition of claim 1 wherein the lower alkylamine nitrate ismethylamine nitrate.

3. The composition of claim 2 wherein the inorganic salt is ammoniumnitrate.

4. The composition of claim 3 wherein the ammonium nitrate is ofparticle size sufficiently small to substantially completely pass a meshscreen.

5. The composition of claim 1 wherein the amount of water is in therange of from about 5 to about 6. The composition of claim 1 wherein theamount of lower alkylamine nitrate is in the range of from about 10 toabout 7. The composition of claim 3 wherein the amount of ammoniumnitrate is in the range of from about to about 90%.

8. The composition of claim 1 wherein the amount of sensitizing materialis in the range of from about 0.1 to about 6.0% by weight based on theweight of the composition.

9. The composition of claim 8 wherein the sensitizing material is apolymerized thermosetting resin selected from the group consisting ofphenol formaldehyde and urea for-maldehyde in the form of thin-walled,hollow, spherical balloons.

TAB LE 1 Composition A B Ammonium nitrate- Guar gum The aboveformulations were prepared as follows: The methylamine nitrate and waterwere placed in a mixing machine and the mixer was operated until asolution was formed. The ammonium nitrate, resin balloons and guar 10.The composition of claim 8 wherein the sensitizing material is bagasse.

11. The composition of claim 1 wherein the thickening agent is guar gum.

12. The composition of claim 1 wherein the inorganic salt is sodiumnitrate.

References Cited Clark 149-92 X Egly et al 149-47 X Fox 149-92 X Egly149 s9 X Scott 149-89 X Minnick 149-89 X CARL D. QUARFORTH, PrimaryExaminer. S. J. LECHERT, JR., Assistant Examiner.

